This invention relates to the fabrication of mercury switches.
A mercury switch typically comprises a contact member which is contacted by an armature activated by some magnetic means in order to close the switch. A layer of mercury coats the armature and contact member in order to provide a low resistance contact. The elements of the switch are sealed within a glass tube. The tube also includes a pool of mercury which replenishes the mercury depleted from the armature and contact area. The switches are usually fabricated by including a ball of mercury and desired dopants in the glass tubes and then activating the switches by rotating them while heating in a furnace to permit the mercury to wet the armature and the contact member, and to permit the dopants to react with the members to form any desired protective layers.
In a typical prior art method of switch activation, each switch is loaded into an individual compartment of a block which includes many compartments. Each compartment is approximately the same size as a switch. The block is then inverted over a fixture which also has individual compartments corresponding to those of the block, so that each switch falls into its individual fixture compartment. Each fixture compartment can be the same size as, or slightly larger than, the switch. The fixture is covered and then rotated on a pair of rollers in a furnace, typically at a temperature of approximately 420.degree. F. for 3 hours where the roller speed is 250 RPM.
While adequate, such a process for activating the switches is time consuming in the loading operation. In addition, the fixture, which is typically made of stainless steel, takes a fairly long period of time to heat up and cool down (typically, approximately 25-30 minutes).
It is, therefore, an object of the invention to provide a more efficient method of fabricating mercury switches.